They are pretty tough.. There were a few mobs that gave me some trouble. I don't think I've ever made it through an encounter with all characters conscious. On one occasion all I had left was the fighter but he triumphed - barely. (that's all I need for a win though.) Chanter chanting, mage blasting spells, cleric blasting spells.. I go all out if a fight seems tough. Lots of pausing, casting, drinking potions. Use every thing at your disposal because you can always rest afterwards. ..
Seems like they really like to go for the mage so keep him moving about and far away so he doesn't auto initiate close combat.. (and then get killed when you try to run away.)